1. Field of the Invention
The present invention relates to an apparatus and a method for producing semiconductors, particularly to a semiconductor producing apparatus and method which are suited for conducting desired etching on semiconductor wafers.
2. Description of the Related Art
Referring to the accompanying drawings, FIG. 6 is a schematic illustration of a typical conventional etching system. In the drawing, reference numeral 1 indicates an etching unit which etches the wafer (semiconductor wafer) by making use of plasma generated under reduced pressure. Here, the wafer is worked in conformity to the mask pattern formed on said wafer. Numeral 2 designates an ashing unit which removes the mask remaining on the wafer immediately after etching by ashing process. Numeral 3 is a wafer transport means whereby the wafers contained in a cassette 5 are transported to said units. Numeral 4 refers to a wafer, such as a semiconductor wafer, which is to be etched, and numeral 5 denotes a wafer cassette, which is a jig for transporting the wafers such as semiconductor wafers to be etched. Approximately 25 sheets of wafer are contained in each cassette which is properly set in the etching system 6.
Traffic line C in the drawing indicates the wafer transport route, which shows an example of the order of treatment conducted on each wafer. On completing the etching treatment, the wafer is put back in the cassette 4 and carried to the next step such as wetting. The wafer is then transported to an inspection step such as dimensional inspection. Here, the result of etching work can be known for the first time.
FIG. 7 is a diagram (flow chart and time chart) showing a process of treatments of a wafer (semiconductor wafer) by the said conventional etching system 6.
In step 1, measurements (measurement of size, etc.) of the wafer to be treated are made. Measurements are conducted on the lot base (for the group of wafers contained in each cassette) or on the sheet-by-sheet base. In step 2, the said wafer cassette (including FOUP (front opening unified pod)) is transported to and set in position in the etching system 6. In step 3, etching and ashing are carried out by operating the etching and ashing units 1 and 2. In this operation, the sheet wafers are taken out one by one from the cassette and transported to the etching unit 1 for etching. On completing the etching work by the etching unit 1, the wafer is carried to the ashing unit 2 one by one by the transport means 3 and ashed by said unit 2. The wafer which has finished the ashing treatment is then placed in the cassette 5. In step 4, the wafer-loaded cassette 5 is taken out and transported to a wetting unit not shown. In step 5, the wafer is subjected to a wetting treatment (e.g., for peeling of the side wall) by the wetting unit. In step 6, the wafer-containing cassette is transferred to a measuring device not shown, and in step 7, the post-treatment measurement of size is made.
In the course of etching work, a protective film is formed on the side of the element as shown in FIG. 1, and in some cases, the thickness of this film becomes unnegligibly large vis-à-vis to the controlled value of CD. Therefore, even if an integrated measuring instrument for measurement of CD is incorporated in the etching system, the result of measurement may be affected by the disturbance induced by said protective film, jeopardizing high-precision control of CD. Thus, the results from said integrated measuring instrument may not provide significant data as an index for the control of the above-said and other working steps.
Further, in the conventional system, as shown in FIG. 6, both etching unit 1 and ashing unit 2 are provided in the system 6, and each wafer is transported between them by a transport means.
Also, each working unit is basically designed to perform treatment on the lot base, that is, according to this system, only after the whole number (lot) of the wafers contained in a cassette have been finished with one treatment, they are allowed to proceed to the next treatment step. Thus, the treatment by each working unit is conducted on the lot base as shown by the time chart of FIG. 7. Therefore, according to this system, even if a failure or fault should be detected in step 7 (step for post-treatment measurements) which is the final step, the etching treatment for that lot is already finished, and there is a possibility that many non-conforming wafers exist in the lot.
The present invention has been made in view of these problems, and it provides a semiconductor producing apparatus and a process therefor according to which the results obtained from the integrated measuring instrument in the etching system can be put to good use as an index for the control of the said and other treating steps, and further, any failure in any working unit such as etching unit is detected in an early stage to reduce the loss of the wafers and the loss of the working time.
In order to solve the above problems, the present invention has incorporated the following means. That is, the semiconductor producing apparatus according to the present invention comprises an integrated measuring instrument for measuring the form or size of the element to be formed into a wafer, an etching unit for etching said wafer by making use of plasma generated under reduced pressure, an ashing unit for ashing said etched wafer, a wetting unit for wetting the etched wafer, a drying unit for drying the wafer which has finished said wetting treatment, a transport means by which said wafers taken into a wafer cassette are transported successively one by one to said integrated measuring instrument and said treating units, and a transport chamber in which said integrated measuring instrument, etching unit; ashing unit, wetting unit, drying unit and transport means are connected to a transport passage designed to be capable of being reduced in pressure, and which is provided with a wafer cassette inlet for receiving the cassette containing a plural number of sheets of wafer to be etched.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.